Usable Length of USB Cable

Discussion in 'Computers, Hardware, and Operating Systems' started by KK4NSF, Nov 6, 2019.

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  1. KK4NSF

    KK4NSF Ham Member QRZ Page

    OK... here is one I bet has not been asked here in recent years: How long a run can you use on a USB cable before the power / signal begins to degrade? The longest I've used is ~25ft, with no problems.... but what if I need to use 100ft?
  2. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    Depends entirely on the bandwidth & speed required. The official USB 2.0 spec is 5 meters (16.5 feet). For maximum speed, you should consider using a good-quality extender if you exceed that length. USB 3.0 is shorter at 3 meters. USB-C length limitations are 1m for USB 3.1 if you want full features - 3m for USB 3.0 and 4m for USB 2.0, all using USB-C type cables

    I strongly doubt you'd get much of anything to work on USB 3.0 at 100 feet. Not likely to work on on USB 2.0 either. At least not reliably or quickly.

    KG5ILR, KK4NSF, KS2G and 1 other person like this.
  3. KK4NSF

    KK4NSF Ham Member QRZ Page

    that's along the lines I was thinking. I'll look into the use of an extender.

  4. W9GB

    W9GB Ham Member QRZ Page

    IF you need 100 feet .... THEN you should be using Ethernet (90 meter / 300 feet length limitation). You could use Hubs & Repeaters, BUT that quickly adds $$$ (Not cheap solution).
    Numerous STANDARDS are Written ... following Basic Principles (Physics and Electricity)[0]=40&items_per_page=50#usb20spec

    The USB 2.0 specification limits the length of a cable between USB 2.0 devices (Full Speed or Hi-Speed) to 5 meters (or about 16 feet and 5 inches).
    In other words, you cannot just connect a bunch of extension cables together (like taking a 6 foot cord and extending it with four (4) other 6 foot extension cords) and run them 30 feet to another room.

    The USB 3.0/3.1 specification does not specify a maximum cable length between USB 3.0/3.1 devices (SuperSpeed or SuperSpeed+), BUT there is a recommended length of 3 meters (or about 9 feet and 10 inches). However, the biggest limitation to the length of the cable is the quality of the cable.

    USB 2.0 compliant cable is sold in TWO versions.
    * All four (4) conductors are 28 AWG
    * Two (2) conductors [data] are 28 AWG and two (2) conductors [power] are 24 AWG.
    This second cable, with larger conductors for Power, are used for powering devices requiring 2 Amps.

    USB Cable Length Limitation : Your Cable Store
    KK4NSF likes this.
  5. KK4NSF

    KK4NSF Ham Member QRZ Page

    Actually, I did it in a similar but different way: I used a R Pi, a powered USB hub and a long crossover cable back to the main computer.... then SSH'd the control function. It sounds more complicated when I write it down, but it was easy as Pi. ;)

    It seems to work ok at 100ft in the little test I did a few hours ago.
  6. AA7QQ

    AA7QQ Ham Member QRZ Page

    If I remember right, you may be able to use USB to ethernet on each end. That way, the CAT5 is doing the long haul.

  7. AA3EE

    AA3EE Ham Member QRZ Page

    The problem with long lengths in USB is due to the timing in the protocol. Any active extender basically starts the protocol over at the other end.
    You might be able to cheat attenuation with a larger diameter conductor, but you can't cheat time!
  8. KA9JLM

    KA9JLM Ham Member QRZ Page

    Depending if the USB connection is supplying power, The signal may be fine. (Until you start Transmitting on a radio)

    I would be more worried about voltage drop on a long run it you are powering something.

    Exactly what are you trying to do ?

    USB over Ethernet cable is a can do. The supply voltage can be 12V so that you have 5V at the end of the long cable. But you still may have problems with RF getting into it.

    Sometimes WiFi is a better choice if you plan on transmitting nearby.

    All wire runs are a good antenna at some frequency.
    Last edited: Nov 9, 2019
  9. KK4NSF

    KK4NSF Ham Member QRZ Page

    I should have clarified my last post: I used an Ethernet crossover cable to connect my main computer to a Pi.... which I then controlled via SSH. at 100ft, no problems

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